Try to surround strings (hoot, story, article) with quotes ':
<div ng-repeat = "data in comments">
<div ng-if="data.type == 'hoot' ">
//different template with hoot data
</div>
<div ng-if="data.type == 'story' ">
//different template with story data
</div>
<div ng-if="data.type == 'article' ">
//different template with article data
</div>
</div>